The present invention refers to a plug-in connection for joining optical fibers or optical waveguides.
In known optical fiber plug-in connections, the tolerances of some precision parts must be less than one micrometer in order to attain low attenuation values. Since in some instances the couplers are disposed in a frame plate and the plugs are located at the rear of a plug-in housing, an axial misalignment and an angular deviation between plug and coupler may occur upon making the plug-in connection for tolerance reasons or due to cable weight and stress forces acting on the cable. In view of their high precision, known plug-in connections allow a compensation of these tolerances only at very small positional deviations. However, a considerably wider tolerance range would be desirable e.g. axial misalignment of up to a few millimeters as well as angular deviations of up to a few degrees between the coupler axis and the plug axis.
An optical fiber plug-in connection of this type is e.g. shown in FIGS. 1 to 3 in which a plug pin 1 is rigidly connected with the respective cable clamp 7 and is insertable in a coupler for connection with a coupler pin 1'. The plug pin 1 and the coupler pin 1' contain a respective optical fiber end and are positioned to each other by a coupler sleeve 2 in such a manner that the fiber ends meet to a sufficient degree. Since optical losses of substantial magnitude are encountered in a monomode fiber upon a misalignment of less than one micrometer, the play between the coupler sleeve 2 and the pins 1, 1' should not exceed about half a micrometer
FIG. 2 depicts the position of the plug relative to the coupler during the plug-in connection. In order to be able to insert the plug pin 1 into the coupler sleeve 2, the respective axes A and B should be aligned as accurately as possible. This is achieved by providing the plug with a centering sleeve 3 which surrounds the plug pin 1, and by providing the coupler with a centering sleeve 4 in which the coupler sleeve 2 is centrally supported. The play between the centering sleeves 3, 4 is of such magnitude that the admissible angle of e.g. 1 degree between the respective mounting sheets 5, 6 is compensated during the plug-in connection. Consequently, there is still a slight misalignment when the plug pin 1 is about to penetrate into the coupler sleeve 2. This misalignment is compensated by floatingly supporting the cable clamp 7 within the centering sleeve 3 and in the plug housing, respectively, the latter not being shown in detail. This play is sufficient to align the plug pin 1 at small lateral misalignment and slight angular differences so as to be able to slide into the coupler sleeve 2. However, as shown in FIG. 3, at greater misalignment, especially at greater angular deviations, a jamming or self-locking occurs.